Find the modulo 4 residue of 121 122 123.

jmc

number theory junior

Problem

Find the modulo 4 residue of

121 \cdot 122 \cdot 123

Solution

121 \cdot 122 \cdot 123 \equiv 1 \cdot 2 \cdot 3 \equiv 6 \equiv 2 (mod 4)

Final answer